Human body communication that transmits and receives communication data through a living body such as a human body has attracted attentions. The human body communication is expected to be applied in medical/health care, near field communication, in-vehicle wireless communication, entertainment, and the like, and can considerably reduce the power consumption compared with conventional ones.
In human body communication, a communication apparatus using a living body as a part of the transmission path are provided with two electrodes. One of the electrodes is a signal electrode connected to a signal line, and the other is a reference potential electrode connected to the ground potential of the communication apparatus having a reference potential. The signal electrodes are connected to each other mainly through a living body, and the reference potential electrodes are connected to each other mainly via space or ground. The communication apparatus thereby transmit the potential difference between the signal electrode and the reference potential electrode.
When the communication apparatus performing human body communication are reduced in size or thickness, the distance between the signal electrode and the reference potential electrode is reduced, and the capacitance of the signal electrode is increased. This can produce a reflection loss and thereby reduce the efficiency.